A group-III nitride semiconductor light-emitting device has a direct-transition-type energy band gap corresponding to the range from visible light to ultraviolet light, and has high emission efficiency. Therefore, the group-III nitride semiconductor light-emitting device has been used as a light-emitting device, such as an LED or an LD.
When the group-III nitride semiconductor light-emitting device is used for an electronic device, it is possible to obtain an electronic device having better characteristics, as compared to when a group III-V compound semiconductor according to the related art is used.
In general, the group-III nitride compound semiconductor is formed by an MOCVD method using trimethylgallium, trimethylaluminum, and ammonia as raw materials.
In the MOCVD method, a carrier gas including the vapor of a raw material is supplied to the surface of a substrate, and reacts with the heated substrate to be decomposed, thereby growing a crystal.
In general, a single crystal wafer made of a group III-V compound semiconductor is obtained by growing a crystal on a single crystal wafer made of a different material. There is large lattice mismatch between the substrate and a group-III nitride semiconductor crystal epitaxially grown on the substrate. For example, when a gallium nitride (GaN) is grown on a sapphire (Al2O3) substrate, there is 16% lattice mismatch therebetween. When a gallium nitride is grown on a SiC substrate, there is 6% of lattice mismatch therebetween.
In general, the large lattice mismatch makes it difficult to epitaxially grow a crystal on the substrate directly. Even though the crystal is grown on the substrate, it is difficult to obtain a crystal having high crystallinity.
Therefore, a metal organic chemical vapor deposition (MOCVD) method has been proposed in which, when a group-III nitride semiconductor crystal is epitaxially grown on a sapphire single crystal substrate or a SiC single crystal substrate, a so-called low temperature buffer layer made of aluminum nitride (AlN) or AlGaN is formed on the substrate and a group-III nitride semiconductor crystal is epitaxially grown on the buffer layer at a high temperature (for example, see Patent Documents 1 and 2).
Studies have been conducted which manufacture a group-III nitride compound semiconductor crystal using sputtering. For example, a method has been proposed which forms a GaN film on the Si (100) plane and the Al2O3 (0001) plane using a radio frequency magnetron sputtering method using N2 gas (for example, see Non-Patent Document 1). In the method disclosed in Non-Patent Document 1, the deposition conditions are as follows: an overall gas pressure of 2 mTorr; a power of 100 W; and a substrate temperature in the range of RT to 900° C. In addition, a sputtering apparatus in which a target and a substrate are arranged so as to face each other is used.
In addition, a method has been proposed which forms a GaN film using an apparatus in which a cathode and a target are arranged so as to face each other and a mesh is interposed between a substrate and the target (for example, see Non-Patent Document 2).
In the method disclosed in Non-Patent Document 2, the deposition conditions are as follows: a pressure of 0.67 Pa in N2 gas; a substrate temperature in the range of 84° C. to 600° C.; a power of 150 W; and a gap of 80 mm between the substrate and the target.
Further, a method has been proposed which forms an AlN film on a substrate in a so-called opposite cathode manner in which targets face each other (for example, see Non-Patent Document 3).
Furthermore, a method of forming an AlN film on a substrate using DC magnetron sputtering has been proposed (for example, Non-Patent Document 4). In the method disclosed in Non-Patent Document 4, the substrate faces the target, and sputtering is performed in a mixed gas atmosphere of Ar and N2 under the following deposition conditions: a pressure in the range of 0.2 to 0.8 Pa and a distance in the range of 60 to 180 mm between the substrate and the target.
Further, as a method of forming an AlN layer as a buffer layer using deposition methods other than an MOCVD method and forming a layer on the buffer layer using the MOCVD method, for example, a method has been proposed which forms a buffer layer using an RF sputtering method and grows on the buffer layer a crystal having the same composition as the buffer layer using an MOCVD method (for example, Patent Document 3). However, in the method disclosed in Patent Document 3, it is difficult to obtain a stable and good crystal (see Patent Documents 4 and 5).
Therefore, in order to obtain a stable and good crystal, for example, the following methods have been proposed: a method of forming a buffer layer and performing annealing in a mixed gas atmosphere of ammonia and hydrogen (for example, Patent Document 4); and a method of forming a buffer layer at a temperature of more than 400° C. using DC sputtering (for example, Patent Document 5).
In the methods disclosed in Patent Documents 4 and 5, a substrate is formed of sapphire, silicon, silicon carbide, zinc oxide, gallium phosphide, gallium arsenide, magnesium oxide, manganese oxide, or a group-III nitride compound semiconductor single crystal. Among these materials, an a-plane sapphire substrate is preferable.
[Patent Document 1] Japanese Patent No. 3026087
[Patent Document 2] JP-A-4-297023
[Patent Document 3] JP-B-5-86646
[Patent Document 4] Japanese Patent No. 3440873
[Patent Document 5] Japanese Patent No. 3700492
[Non-Patent Document 1] Y. USHIKU, et al., “Proceedings of the 21st Century Combined Symposium”, Vol. 2, p. 295 (2003)
[Non-Patent Document 2] T. Kikuma, et al., “Vacuum”, Vol. 66, p. 233 (2002)
[Non-Patent Document 3] Kikuo Tominaga, et al., “Japanese Journal of Applied Physics”, Vol. 28, p. 7 (1989)
[Non-Patent Document 4] M. Ishihara, et al., “Thin Solid Films”, Vol. 316, p 152 (1998)
However, the inventors' experiments proved that, when deposition was performed under the conditions disclosed in Patent Documents 4 and 5, it was difficult to obtain a stable and good crystal using a group-III nitride compound semiconductor including Ga as a group-III element. That is, in the methods disclosed in Patent Documents 4 and 5, an MOCVD method is used to form a GaN layer on the buffer layer formed by a sputtering method. When the buffer layer is formed by the sputtering method, deposition rate is high, but the crystallinity of the buffer layer is likely to deteriorate depending on the deposition conditions. When the GaN layer is formed on the buffer layer having low crystallinity by the MOCVD method, there is a concern that the crystallinity of the GaN layer will be greatly reduced.
When a GaN layer is formed by a sputtering method under the conditions disclosed in Non-Patent Documents 1 and 2, it is difficult to form a GaN layer having high crystallinity on the buffer layer.
The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a group-III nitride compound semiconductor light-emitting device that is capable of stably forming a crystal film made of a uniform group-III nitride compound semiconductor in a short time and has high productivity and good emission characteristics, a method of manufacturing a group-III nitride compound semiconductor light-emitting device, and a lamp.
The inventors have conducted studies to solve the above-mentioned problems, thereby achieving the present invention.
That is, the present invention is as follows.
According to a first aspect of the present invention, a method of manufacturing a group-III nitride compound semiconductor light-emitting device includes a step of forming on a substrate a semiconductor layer made of a group-III nitride compound semiconductor including Ga as a group-III element using a sputtering method. The substrate and a sputtering target are arranged so as to face each other, and a gap between the substrate and the sputtering target is in the range of 20 to 100 mm.
According to a second aspect of the present invention, a method of manufacturing a group-III nitride compound semiconductor light-emitting device includes a step of forming on a substrate a semiconductor layer made of a group-III nitride compound semiconductor including Ga as a group-III element using a sputtering method. When the semiconductor layer is formed, power is supplied to a sputtering target by a radio frequency power supply or a pulsed DC power supply.
According to a third aspect of the present invention, a method of manufacturing a group-III nitride compound semiconductor light-emitting device includes a step of forming on a substrate a semiconductor layer made of a group-III nitride compound semiconductor including Ga as a group-III element using a sputtering method. When the semiconductor layer is formed, the pressure of a chamber for sputtering is set to be lower than 1.0×10−3 Pa in advance, and a raw material is supplied into the chamber.
According to a fourth aspect of the present invention, a method of manufacturing a group-III nitride compound semiconductor light-emitting device includes a step of forming on a substrate a semiconductor layer made of a group-III nitride compound semiconductor including Ga as a group-III element using a sputtering method. The substrate and a sputtering target are arranged so as to face each other.
According to a fifth aspect of the present invention, a method of manufacturing a group-III nitride compound semiconductor light-emitting device includes a step of forming on a substrate a semiconductor layer made of a group-III nitride compound semiconductor including Ga as a group-III element using a sputtering method. When the semiconductor layer is formed, a magnetic field is swinged or rotated with respect to a sputtering target.
According to a sixth aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to any one of the first to fifth aspects, preferably, the semiconductor layer is formed by a reactive sputtering method that introduces a nitride raw material into a reactor.
According to a seventh aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to the sixth aspect, preferably, nitrogen is used as the nitride raw material.
According to an eighth aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to any one of the first to seventh aspects, preferably, a buffer layer made of a columnar crystal is formed between the substrate and the semiconductor layer.
According to a ninth aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to the eighth aspect, preferably, the buffer layer is formed by the sputtering method.
According to a tenth aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to the eighth or ninth aspect, preferably, the buffer layer is formed of a group-III nitride compound including Al as a group-III element.
According to an eleventh aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to the tenth aspect, preferably, the buffer layer is formed of AlN.
According to a twelfth aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to any one of the eighth to eleventh aspects, preferably, the buffer layer is formed so as to cover 90% or more of the front surface of the substrate.
According to a thirteenth aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to any one of the eighth to twelfth aspects, preferably, the width of the columnar crystal forming the buffer layer is in the range of 0.1 to 100 nm.
According to a fourteenth aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to any one of the eighth to thirteenth aspects, preferably, the thickness of the buffer layer is in the range of 10 to 500 nm.
According to a fifteenth aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to any one of the eighth to fourteenth aspects, preferably, the buffer layer is formed of AlN, and the semiconductor layer made of the group-III nitride compound is formed of GaN.
According to a sixteenth aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to any one of the first to fifteenth aspects, preferably, the substrate is formed of sapphire.
According to a seventeenth aspect of the present invention, a group-III nitride compound semiconductor light-emitting device is manufactured by the manufacturing method according to any one of the first to sixteenth aspects.
According to an eighteenth aspect of the present invention, a lamp includes the group-III nitride compound semiconductor light-emitting device according to the seventeenth aspect.
According to a nineteenth aspect of the present invention, a method of manufacturing a group-III nitride compound semiconductor light-emitting device includes a step of forming on a substrate a semiconductor layer made of a group-III nitride compound semiconductor including Ga as a group-III element using a sputtering method. When the semiconductor layer is formed by the sputtering method, a bias of not less than 0.1 W/cm2 is applied to the substrate.
According to a twentieth aspect of the present invention, a method of manufacturing a group-III nitride compound semiconductor light-emitting device includes a step of forming on a substrate a semiconductor layer made of a group-III nitride compound semiconductor including Ga as a group-III element using a sputtering method. When the semiconductor layer is formed by the sputtering method, power supplied to a sputtering target is in the range of 0.1 W/cm2 to 100 W/cm2.
According to a twenty-first aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to the nineteenth or twentieth aspect, preferably, the semiconductor layer is formed by a reactive sputtering method that introduces a nitride raw material into a reactor.
According to a twenty-second aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to the twenty-first aspect, preferably, nitrogen is used as the nitride raw material.
According to a twenty-third aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to any one of the nineteenth to twenty-second aspects, preferably, a buffer layer made of a columnar crystal is formed between the substrate and the semiconductor layer.
According to a twenty-fourth aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to the twenty-third aspect, preferably, the buffer layer is formed by the sputtering method.
According to a twenty-fifth aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to the twenty-fourth aspect, preferably, the buffer layer is formed of a group-III nitride compound including Al.
According to a twenty-sixth aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to the twenty-fifth aspect, preferably, the buffer layer is formed of AlN.
According to a twenty-seventh aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to any one of the twenty-third to twenty-sixth aspects, preferably, the buffer layer is formed so as to cover 90% or more of the front surface of the substrate.
According to a twenty-eighth aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to any one of the twenty-third to twenty-seventh aspects, preferably, the width of the columnar crystal forming the buffer layer is in the range of 0.1 to 100 nm.
According to a twenty-ninth aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to any one of the twenty-third to twenty-eighth aspects, preferably, the thickness of the buffer layer is in the range of 10 to 500 nm.
According to a thirtieth aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to any one of the twenty-third to twenty-ninth aspects, preferably, the buffer layer is formed of AlN, and the semiconductor layer made of the group-III nitride compound is formed of GaN.
According to a thirty-first aspect of the present invention, in the method of manufacturing a group-III nitride compound semiconductor light-emitting device according to any one of the nineteenth to thirtieth aspects, preferably, the substrate is formed of sapphire.
According to a thirty-second aspect of the present invention, a group-III nitride compound semiconductor light-emitting device is manufactured by the manufacturing method according to any one of the nineteenth to thirty-first aspects.
According to a thirty-third aspect of the present invention, a lamp includes the group-III nitride compound semiconductor light-emitting device according to the thirty-second aspect.
According to a method of manufacturing a group-III nitride compound semiconductor light-emitting device of the present invention, it is possible to form a uniform crystal film in a short time using a sputtering method. In this way, it is possible to stably form a group-III nitride compound semiconductor layer having high crystallinity. As a result, it is possible to obtain a group-III nitride compound semiconductor light-emitting device having high productivity and good emission characteristics.